drivers/net/ieee802154/atusb.c: s/retval/ret/; clean up zero vs. non-negative
drivers/net/ieee802154/atusb.c: fix TX reentrance protection

We can now send multiple packets.
drivers/net/ieee802154/atusb.c: return LQI; respect tTR13
drivers/net/ieee802154/atusb.c: update to do list; clarify atusb_ed
drivers/net/ieee802154/atusb.c: update to do; set PHY channel default